Pluff Mud, Persistence and Protecting Fragile Ecosystems

Nearly half the oyster reefs in South Carolina have disappeared in the last century.
Professor Caye Drapcho and her students have teamed up with Al Segars ’74
to help Mother Nature.
By Nancy Spitler

It’s a clear Monday morning in May on the banks of the Ashepoo River in an area called Bennett’s Point.

A group of seven Clemson students and their professor, Caye Drapcho, sit inside the Michael D. McKenzie Field Station and listen to a series of presentations about oyster reef construction, living shorelines and stormwater management by Ben Stone and Al Segars ’74, who work for the S.C. Department of Natural Resources.

They had arrived late the night before after a trip from Clemson that was longer than anticipated due to a flat tire, but they’re engaged and eager, knowing they’re about to put the theory of the last semester into practice.

Presentations complete, we apply sunscreen, grab our life jackets and climb onto the boat. We head down the Ashepoo River at a slow pace, with Segars and Stone taking time to talk about estuaries and marshes, and the biological and economical importance of those. You can see along the edge of the river where the shoreline has eroded, some of which is the result of recent hurricanes, which have not treated this area well.

Marshes may evoke only images of mosquitoes and mud, but they are a vital part of our ecosystem. Segars characterizes marshes as “the nursery for all sea life,” and touts their other important functions as well: slowing erosion, filtering impurities before they reach the ocean, mitigating storm surges. Protecting the marshes is not just an ecological imperative, it’s an economic one as well. Marshes are the bedrock of the seafood industry (a $40+ million industry in South Carolina), and they protect inland development from stormy seas and flooding.

We spot dolphins nearby, including two babies just getting the hang of how to smoothly come out of the water and slide back in. Birds are in abundance, and the sky is that kind of blue that reminds you of the best day you ever spent outside on the water.

Oysters not only serve as great items on your menu; they also filter impurities from coastal waters, and oyster reefs provide habitats for fish, shrimp, crabs and other marine life while they slow erosion and protect shorelines.

Globally, 85 percent of oyster reefs have been lost because of overharvesting or habitat degradation. Disease, development and algal flows have contributed to the decimation. In South Carolina, nearly half of our oyster reefs have disappeared in the last century.

If there are no oyster reefs, there’s no place for oyster larvae to settle in and develop.

So scientists and conservationists have been trying to figure out a way to help mother nature — by creating new oyster reefs. Several ways are being tested, and Stone and Segars point them out as we travel down the river. Loose oyster shells can be shot out by a water cannon on a barge. Mesh bags of oyster shells can be stacked (after the shells are quarantined for six months to make sure they are free of disease and “hitchhikers”). Oyster castles are stackable blocks constructed of recycled oyster shells and concrete that provide a hard service to which oyster larvae can attach and begin to grow.

All of these have had some success, but the solution that Stone and Segars have found effective for their uses is elegant in its simplicity. They began using discarded crab traps that they acquired through donations from commercial crabbers and abandoned traps removed by SCDNR personnel or from beach cleanups.

“We close all the funnels on these traps and repair them with zip ties,” said Stone, “so they no longer capture crabs or other marine animals. We then coat them in a thin layer of tile mortar so that it creates a hard surface for larval oysters to attach to and grow into new oyster reefs.” The crab traps are then placed in groups in the pluff mud during the spring and summer months when the oysters are spawning to increase the chances of attracting larval oysters to attach. Fastened down with re-bar, they slowly create new oyster reefs which provide additional ecological benefits. The structure absorbs waves, and as the waves roll over it, the sediment drops behind it, rebuilding the marsh land behind the reefs.

It’s a good but not perfect solution. It’s labor-intensive, and there’s work to be done in figuring out the best coating to ensure maximum attachment. So in 2012, Segars contacted Drapcho, a biosystems engineering professor at Clemson, to ask if her students might be interested in exploring the best surface material for manufactured oyster substrate — “developing a better mousetrap,” as he puts it. Their constraints? “It has to be inexpensive and fairly simple.”

TACKLING BIGGER ISSUES

Segars was a veterinarian in the town of Hartsville, South Carolina, when he and his wife decided they needed a mid-life change. They packed the family up and moved to Beaufort, and Segars convinced the DNR they needed a veterinarian. He’s been here ever since. His title is stewardship coordinator for the ACE Basin National Estuarine Research Reserve and veterinarian for DNR. You get that feeling that his job description includes a large portion of “other duties as needed.”

He’s passionate not only about the wildlife, but also the environment in which it lives — the river, the marsh, the coastlines. He says that people are beginning to realize that the marsh is worth saving, both for storm surge protection as well as for the sea life it nourishes. It’s a change from a small-town vet’s practice. “We’re tackling big issues here,” he says, “things that will impact my kids and your kids.”

Drapcho, an associate professor of biosystems engineering, has a similar enthusiasm for tackling the world’s challenges. She got into biosystems engineering because it takes a systems approach — “not looking at things in tunnel vision, but looking at the whole.” It’s also at the intersection of her passions. “You remember the slogans, ‘Save the Whales’ and ‘Feed the World’? Those were the things I was passionate about,” she says. “I think biosystems engineering is the intersection of those two. You can save people by saving the resources that sustain them.”

She pauses. “I get renewed when we can reinvigorate students to have those goals,” she says.

Drapcho earned her Ph.D. at Clemson, then taught for several years at LSU before returning to teach at Clemson. She had colleagues at LSU working with oyster reef restoration and was familiar with their research, so after Segars contacted her, she took a small group of students to the Rockefeller Wildlife Refuge in Louisiana to observe the work being done there. In the fall of 2012, a senior design team began working to solve the problem, using the abandoned crab traps and coating them. They field tested their coated structures at the wildlife refuge.

That spring, a Creative Inquiry (CI) class formed and began studying the issue and exploring solutions. Creative Inquiry courses are designed to continue for multiple semesters. So in the semesters to follow, the students researched possible coatings, water quality and carbon sequestration (oysters store carbon as they form their shells). One year, the team made all kinds of different models and shapes, trying to get the maximum surface area and ease of fabrication. Over the semesters, they tested the wire structures, coated and uncoated in water of various levels of salinity to measure how much they would rust.

Our trip was the culmination of that research. On the boat with us were small coated and uncoated wire structures they had built. We were headed to a spot on Fenwick Island where they would work with other DNR staff to put a group of prepared crab traps in place, and then fasten the test structures to those with zip ties.

The Work and the Waiting

We meandered out slowly to the island, most of which has been acquired recently by The Nature Conservancy and is being sold to South Carolina DNR. It was low tide, so the mud at the edge of the river was exposed for 20-25 feet beyond the marsh grass. We tied off the boat at the dock and were met by three DNR staffers who had come, bringing the treated crab traps, rebar and zip ties for installation as soon-to-be oyster reef.

One had on waders; from a distance, a second looked like he might have on waders. Up close you realized it was just a coating of brown pluff mud from sinking up to his knees.

At Fenwick Island, marsh grass grows out from the land to where the pluff mud begins. If you haven’t been introduced to pluff mud, it’s that kind of soupy molasses-type mud that will suck your shoes off when you try to take a step. The smell generally reaches your nose just before you catch sight of it. Pat Conroy described it as the smell of the South in heat. There are some who believe you can coat yourself with it to hold off the mosquitoes. Others would rather suffer the bites.

The students piled out of the boat onto the dock, marched up to the island, and then received instructions on how the traps would be installed and a few other details for dealing with pluff mud: Make sure your shoes are tied tightly. If you lift your heel first when you try to lift your foot, it’s easier.

Then they trooped out across the marsh grass and toward the crab traps that needed to be situated and tacked down in place with rebar. When they hit the pluff mud, they sunk up to their knees. Some were more timid than others, but before long, they were all working together, passing crab traps toward the edge of the marsh, placing them on the mud at the edge of the river. Periodically, they fell, laughed, picked themselves up and kept going.

Before they were finished, a line of crab traps, two and three deep and about 30 feet long, lined the shore of the Ashepoo River, waiting for oysters to land and attach and begin to develop. Two students went back to the dock to retrieve their set of miniature wire structures, half plain wire, half coated with a spray concrete mixture. They had tested both in a mixture of salt water, but hadn’t subjected them to the type of treatment the tide provides each day.

They zip-tied the trial boxes to the crab traps, then gathered for a picture. They trooped back through the pluff mud to the dock, not as shy or tentative as before. They tossed their shoes in a bucket, then dangled their feet off the dock, washing as much of the mud as possible back into the river.

As we climbed into the boat and left the dock, the clock started on the experiment. In about six months, another group of CI students, possibly some of the same ones, will return to Fenwick Island and see what has happened. Are the structures covered with oyster shells and developing oysters? Have they rusted away? Is one type working better than the other? Are the shorelines growing out and encompassing the reefs, adding another layer of protection for the fragile ecosystem?

Then they’ll take their newly acquired knowledge and return to Clemson, using that knowledge to try again to take another step in building “a better mousetrap.”